Adsorption apparatus used as an electro-heating storage

ABSTRACT

Periodic adsorption apparatus with the substance pair zeolite/water being used as electro-heat storage devices. Due to the heat pumping effect there can be a 30% savings of power.

This is a divisional of co-pending application Ser. No. 695,484 filed onJan. 28, 1985 U.S. Pat. No. 4,802,341.

Background of the Invention

The invention relates to an adsorption apparatus with heat pumpingeffect used as an electro-heating storage.

In order to smooth the severely fluctuating current use, electro-heatstorages are employed. When rates for electrical current areeconomically favorable, typically a storage material, like ceramic, castiron, oil or water is heated, for example, during the charge phase. Thestored heat is fed to the consumer via suitable heat removing systemsduring the subsequent discharging phase. Night time current storages arein use for heating individual rooms and central heat storages whichsupply a plurality of consumers from one location through a heatdistribution system. In order to keep the space requirement for theelectro-heat storages as low as possible, the storage materials arepartially heated to a temperature above 900° C. Undesirable heat lossesmust be prevented with expensive insulation measures. A heat pumpingeffect with a corresponding energy saving is not possible with thesedevices.

Zeolites are solid alumini-silicates with a uniform crystal structure.Adsorption zeolites have the characteristics of being able to adsorb aconsiderable amount of water in its crystal structure. Heat is releasedduring this adsorption. In order to again desorb the water, heat must beused.

Heat storage installations with the adsorption pair of zeolite/water aresuggested in German laid open patent applications P 32 07 656 and P 3212 608. When the rates for electrical current are low steam is desorbedfrom the absorption zeolith and liquified in a condenser. Thecondensated steam is again evaporated at a later time by absorbingambient heat and adsorbed in the adsorption substance by releasing heatat high temperatures. The control of such installations is only possibleby a plurality of valves or check valves with corresponding controlunits. This control effort is not economical with small electro-heatstorages despite a 30% saving of energy.

Summary of the Invention

It is, therefore, an object of the invention to use periodic adsorptionprocesses as electro-heat storages and to save energy by means ofavailable pump effect.

The adsorption electro-heat storage in accordance with the inventionconsists of the conventional parts electro heating, heat removal systemand control, on the one hand, and the adsorption part, on the otherhand. The adsorption part consists of two containers which are connectedby means of a steam line; namely the adsorption substance containerwhich in the conventional part of the electro-heat storage replaces thestorage material and the collecting container for condensate. A steamline leads from the containers to a condenser and a water cycle leads toa heat collector. The water cycle contains a pump. The mode of operationis divided into two phases;

(a) charging phase - the adsorption substance container is heated to200°-300° C. by means of the electro-heater. Thereby, steam is desorbedfrom the adsorption substance which is liquified in the condenser andflows as a condensate into the collecting container. The condensationheat is discharged as an operating heat at temperatures up to 100° C.;

(b) discharge phase - the electro-heater is out of operation. Heat isremoved from the adsorption substance container through the conventionalheat removal system. Condensate evaporates in the collecting containerduring lower steam pressures and cools the remaining water. The steam isexothermically adsorbed by the adsorption substance at hightemperatures. The adsorption heat can be removed through the heatremoval system if so desired. The pump of the water cycle feeds cooledresidue condensate through the heat collector. So that the water cycledoes not dissipate heat to the heat collector, a control unit actuatesthe pump only when the temperature in the heat collector is higher thanthe condensation temperature in the collecting container. Moreover, theoperation of the pump may be made dependent from other criteria throughthis control unit. For example, the pump may only be operated after acertain temperature had been exceeded in the heat collector.

This process can be advantageously used for safety against frost or formaintaining a certain temperature of the exhaust heat (for example,waste water, cooling air).

The possibility exists in conventional electro-heat storages for roomheating to aftercharge the heating storage with current during thedaytime on extremely cold days. Since during these very cold days theheat reception through the heat collector may be limited, an afterchargeis advantageously transmitted to the system through an electrical heaterin the collecting container. Thereby, the heat dissipation capacity fromthe adsorption electro-heating storage increases by about 30% withrespect to the aftercharge capacity, since the adsorption of the steamin the adsorption substance releases the chemically stored adsorptionheat.

The adsorption electro-heat storage in accordance with the invention canbe advantageously integrated into a tile hearth. In this case, hotcombustion gases take over the desorption operation from case to case.In this manner, the tile hearth can store more heat and recoveradditional heat through the heat collector. The cooling time of thetiled hearth is prolonged.

A further advantageous possibility of use is the coupling of anadsorption electro-heat storage with a hot water storage. The adsorptionpart recovers additional heat through the heat pumping effect from theair or the waste water and permits a small structural size of the waterstorage. The use of night current is also advantageous for the utilitycompany during the summer time.

Adsorption apparatuses operate at least partially under vacuumconditions. A sufficient tightness of the system is the basicrequirement for a smooth operation. It is therefore suggested toassemble the adsorption part as a compact, finished apparatus part bythe manufacturer. When using the heat collector as an outside absorber,it must be pushed through the building wall to the outside, while theremainder of the device components remain within the building. For thispurpose, a wall box is built into the building wall which is closed witha suitable insulation element during the installation of the device.This insulation element fixed the heat collector to the outside andleaves room on the inside for the flexible condensation lines to thecollecting container.

In a further advantageous development the insulation element is providedwith a ventilation system which feeds hot exhaust air from the buildingto the outside positioned heat collector for recovery.

The zeolite types Na-A, Mg-A, Na-Y, H-Y and Na-X have been shown to beuseful as adsorption substances. They have very good adsorptioncharacteristics for water in addition to a sufficient temperature andcycle stability.

The condensate in the collecting container may freeze due to theevaporation operation. The latent heat which is thereby released can beadditionally used for the adsorption heat in the adsorption substanceduring increased temperatures. In a sufficiently large dimensionedcollecting container, the total evaporation enthalphy may be supplied bythe latent conversion heat. The ice which is generated in the dischargephase is again molten during the condensation heat. About 1.3 Kilogramwater is required per Kilogram of adsorption substance.

If no conversion heat is to be used and when heat is coupled in throughthe heat collector from the environment at temperatures below 0° C., anantifreeze agent may be added to the water. Suitable substances aresalts or lyes which have a low steam pressure.

If only ambient heat is collected above 0° C., no antifreeze agents arerequired. The heat collector may be installed above the maximum waterlevel in the collecting container, so that the heat collector does notfreeze during the frosty weather. The water would then return into thecollecting container when the pump is in the rest position. A watersyphon in the water cycle prevents a condensation of steam in the heatcollector during the charge phases and also prevents a loss of heat tothe outside.

The described adsorption electro-heat storage does not contain anyvalves and requires only a small control effort for the control of thepump. The costs for power are lower by about 30% with respect to theconventional systems. The electrical connecting line is reduced by aboutone third.

Ventilation heat losses can be reduced by a simple heat recovery of theexhaust air. Since all components of a conventional electro-heat storagecan be used, with the exception of the storage material, only a smallamount of additional cost is incurred. A heat pumping installation withheat recovery possibilities is obtained from a pure heat storage devicewith a favorable control. During the discharge phase the new system isalways ready to absorb ambient heat, in contrast to other heat pumpingsystems, no matter how high the temperatures and amounts are. Even thesmallest heat amounts can be used without limitation.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplified embodiments of the invention are illustrated in the drawingand are described in more detail in the following. In the drawings:

FIG. 1 - an adsorption electro-heat storage for room heating; and

FIG. 2 - an adsorption electro-heat storage in combination with a hotwater storage.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows an adsorption substance container 1 on which a smallcollecting container 2 is connected. From there, a steam line 3 leads toa condenser (4) and two flexible liquid lines 5 leads to a heatcollector 6. The associated water cycle contains a pump 7. The operationis divided into two phases:

a. Charge Phase

The adsorption substance container is heated to a temperature of250°-300° C. by means of electric heating rods 8. During this time wateris evaporated from the adsorption substance. The steam can condense incondensator 4 and dissipate heat to the room air. The condensate flowsinto the collecting container 2 and remains there until the dischargephase.

b. Discharge Phase

The adsorption substance container is cooled by the air flow. During alowering of the adsorption substance temperature there is also alowering of the steam pressure in the containers. Water from thecollecting container gets cold and the adsorption substance hot.Whenever the water temperature in the collecting container 2 falls belowthe outer temperature pump 7 pumps water through the heat collector. Thecold water absorbs heat from the outer air and transfers it to theevaporating water in the collecting container 2.

FIG. 2 shows a combination of an adsorption electro-heat storage with ahot water storage. Condenser 24 is mounted within the hot water storage28. During the charging phase the condenser dissipates the condensationheat to the water storage 28. During the discharge phase the operatingheat is transferred from the adsorption substance container 21 through awater-steam-system to the water. When the storage water is too cold, thevalve 29 opens. Water flows from container 30 to the evaporator 31 andevaporates therein. The steam dissipates the condensation heat in theliquefier 32. The condensate again collects in container 30.

Thus, the several aforementioned objects and advantages are mosteffectively attained. Although several somewhat preferred embodimentshave been disclosed and described in detail herein, it should beunderstood that this invention is in no sense limited thereby and itsscope to be determined by that of the appended claims.

We claim:
 1. A process for operating a periodic adsorption apparatus foruse as an electro-heat storage provided with a heat pumping effect, saidperiodic adsorption apparatus being characterized by a charge phase anda discharge phase of operation, said process comprising the steps:during said charge phase of operation,(a) desorbing water from anadsorption substance contained in an adsorption substance container,employing heat produced from a heat producing source so as to producevapor; (b) liquifying said vapor into water using a condenser therebyliberating condensation heat; and (c) discharging said condensation heatas operating heat and collecting said water in a collecting container;and during said discharge phase, (d) removing heat from said adsorptionsubstance so that thereupon a portion of said water in said collectingcontainer evaporates and is exothermically absorbed in said adsorptionsubstance, while a residual portion of said water remains in saidcollecting container; and (e) pumping said residual portion of waterthrough a heat collector using a pump, so that said residual portion ofwater in said heat collector absorbs heat from a heat flow presented ina heat exchanging relationship with said heat collector.
 2. The processin accordance with claim 1, wherein step (e) further comprises using acontrol unit to enable said pump to commence pumping said residualportion of water through said heat collector at a time when thetemperature in said heat collector is higher than the temperature ofsaid residual portion of water in said collecting container.
 3. Theprocess in accordance with claim 2, wherein step (e) further comprisesenabling the operation of said pump only after the temperature of saidheat collector reaches a preselected temperature value.
 4. The processin accordance with claim 1, wherein step (e) further comprises:pumpingsaid residual portion of water through said heat collector which isconnected in fluid communication with said collecting container and saidpump through a water cycle, said heat collector being capable ofexchanging heat from a supply of waste water to said water cycle, andtransferring heat from said waste water to said water cycle.
 5. Theprocess in accordance with claim 1, wherein step (d) further comprises,during said discharge phase, temporarily heating said water in saidcollecting container using an electric heating device.
 6. The process inaccordance with claim 1, which further comprises prior to step (a),installing said adsorption substance container in an integrated mannerin a tile hearth capable of producing heat containing combustion gases,and wherein step (b) further comprises desorbing water from saidadsorption substance using the heat provided by said heat containingcombustion gases.
 7. The process in accordance with claim 1, whereinstep (c) process further comprises:heating said water in a hot waterstorage using said condensation heat, and wherein step (d) comprisesusing a water-steam system to discharge the heat liberated from saidadsorption substance, for heating and evaporating a portion of saidwater during said discharge phase of operation.
 8. The process inaccordance with claim 4, wherein prior to step (e), said process furthercomprises providing heat containing exhaust air to said heat collector,and transmitting the heat content of said exhaust air through said watercycle into said collecting container.